Is there any way to specify a suggested filename when using data: URI?

If for example you follow the link:


The browser will prompt you to download a file consisting of the data held as base64 in the hyperlink itself. Is there any way of suggesting a default name in the markup? If not, is there a JavaScript solution?

Use the download attribute:

<a download='FileName' href='your_url'>

Live example on

Currently works on Chrome, Firefox, Edge, Opera, and desktop Safari but not iOS Safari or IE11.

Chrome makes this very simple these days:

function saveContent(fileContents, fileName)
    var link = document.createElement('a'); = fileName;
    link.href = 'data:,' + fileContents;;

HTML only: use the download attribute:

<a download="logo.gif" href="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7">Download transparent png</a>

Javascript only: you can save any data URI with this code:

function saveAs(uri, filename) {
  var link = document.createElement('a');
  if (typeof === 'string') {
    link.href = uri; = filename;

    //Firefox requires the link to be in the body
    //simulate click;

    //remove the link when done
  } else {;

saveAs(file, 'logo.gif');

Chrome, Firefox, and Edge 13+ will use the specified filename.

IE11, Edge 12, and Safari 9 (which don't support the download attribute) will download the file with their default name or they will simply display it in a new tab, if it's of a supported file type: images, videos, audio files, …

According to RFC 2397, no, there isn't.

Nor does there appear to be any attribute of the <a> element that you can use either.

However HTML5 has subsequently introduced the download attribute on the <a> element, although at the time of writing support is not universal (no MSIE support, for example)

I've looked a bit in firefox sources in netwerk/protocol/data/nsDataHandler.cpp

data handler only parses content/type and charset, and looks if there is ";base64" in the string

the rfc specifices no filename and at least firefox handles no filename for it, the code generates a random name plus ".part"

I've also checked firefox log

[b2e140]: DOCSHELL 6e5ae00 InternalLoad data:application/octet-stream;base64,SGVsbG8=
[b2e140]: Found extension '' (filename is '', handling attachment: 0)
[b2e140]: HelperAppService::DoContent: mime 'application/octet-stream', extension ''
[b2e140]: Getting mimeinfo from type 'application/octet-stream' ext ''
[b2e140]: Extension lookup on '' found: 0x0
[b2e140]: Ext. lookup for '' found 0x0
[b2e140]: OS gave back 0x43609a0 - found: 0
[b2e140]: Searched extras (by type), rv 0x80004005
[b2e140]: MIME Info Summary: Type 'application/octet-stream', Primary Ext ''
[b2e140]: Type/Ext lookup found 0x43609a0

interesting files if you want to look at mozilla sources:

data uri handler: netwerk/protocol/data/nsDataHandler.cpp
where mozilla decides the filename: uriloader/exthandler/nsExternalHelperAppService.cpp
InternalLoad string in the log: docshell/base/nsDocShell.cpp

I think you can stop searching a solution for now, because I suspect there is none :)

as noticed in this thread html5 has download attribute, it works also on firefox 20

The following Javascript snippet works in Chrome by using the new 'download' attribute of links and simulating a click.

function downloadWithName(uri, name) {
  var link = document.createElement("a"); = name;
  link.href = uri;;

And the following example shows it's use:

downloadWithName("data:,Hello%2C%20World!", "helloWorld.txt")


The entire purpose is that it's a datastream, not a file. The data source should not have any knowledge of the user agent handling it as a file... and it doesn't.

you can add a download attribute to the anchor element.


<a download="abcd.cer"

Look at this link:


It even works (as in, doesn't cause a problem) with ;base64 at the end
like this (in Opera at least):


Also there is some info in the rest messages of the discussion.

Using service workers, this is finally possible in the truest sense.

  1. Create a fake URL. For example /saveAs/myPrettyName.jpg
  2. Use URL in <a href, <img src, url ), absolutely anything that can be done with a "real" URL.
  3. Inside the worker, catch the fetch event, and respond with the correct data.

The browser will now suggest myPrettyName.jpg even if the user opens the file in a new tab, and tries to save it there. It will be exactly as if the file had come from the server.

// In the service worker
self.addEventListener( 'fetch', function(e)
    if( e.request.url.startsWith( '/blobUri/' ) )
        // Logic to select correct dataUri, and return it as a Response
        e.respondWith( dataURLAsRequest );

There is a tiny workaround script on Google Code that worked for me:

It adds a form with the data in it, submits it and then removes the form again. Hacky, but it did the job for me. Requires jQuery.

This thread showed up in Google before the Google Code page and I thought it might be helpful to have the link in here, too.

It's kind of hackish, but I've been in the same situation before. I was dynamically generating a text file in javascript and wanted to provide it for download by encoding it with the data-URI.

This is possible with minormajor user intervention. Generate a link <a href="data:...">right-click me and select "Save Link As..." and save as "example.txt"</a>. As I said, this is inelegant, but it works if you do not need a professional solution.

This could be made less painful by using flash to copy the name into the clipboard first. Of course if you let yourself use Flash or Java (now with less and less browser support I think?), you could probably find a another way to do this.

Here is a jQuery version based off of Holf's version and works with Chrome and Firefox whereas his version seems to only work with Chrome. It's a little strange to add something to the body to do this but if someone has a better option I'm all for it.

var exportFileName = "export-" + filename;
$('<a></a>', {
    "download": exportFileName,
    "href": "data:," + JSON.stringify(exportData, null,5),
    "id": "exportDataID"

This one works with Firefox 43.0 (older not tested):


function download() {
  var msg="Hello world!";
  var blob = new File([msg], "hello.bin", {"type": "application/octet-stream"});

  var a = document.createElement("a");
  a.href = URL.createObjectURL(blob);



<html lang="en" xmlns="">

    <meta charset="utf-8"/>
    <script type="text/javascript" src="dl.js"></script>

<button id="create" type="button" onclick="download();">Download</button>

If button is clicked it offered a file named hello.bin for download. Trick is to use File instead of Blob.


var isIE = /*@[email protected]*/false || !!document.documentMode; // At least IE6
var sessionId ='\n';
var token = '\n';
var caseId = CaseIDNumber + '\n';
var url = casewebUrl+'\n';
var uri = sessionId + token + caseId + url;//data in file
var fileName = "file.i4cvf";// any file name with any extension
if (isIE)
            var fileData = ['\ufeff' + uri];
            var blobObject = new Blob(fileData);
            window.navigator.msSaveOrOpenBlob(blobObject, fileName);
    else //chrome
        window.requestFileSystem = window.requestFileSystem || window.webkitRequestFileSystem;
         window.requestFileSystem(window.TEMPORARY, 1024 * 1024, function (fs) {
            fs.root.getFile(fileName, { create: true }, function (fileEntry) { 
                fileEntry.createWriter(function (fileWriter) {
                    var fileData = ['\ufeff' + uri];
                    var blob = new Blob(fileData);
                    fileWriter.addEventListener("writeend", function () {
                        var fileUrl = fileEntry.toURL();
                        var link = document.createElement('a');
                        link.href = fileUrl;
               = fileName;
                    }, false);
                }, function () { });
            }, function () { });
         }, function () { });

You actually can achieve this, in Chrome and FireFox.

Try the following url, it will download the code that was used.